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The correct OPTION is (b) 600°C

The best explanation: Cast irons, upon the removal of WELDING HEAT, get solidified very quickly. This solidification TAKES place due to the surrounding cold mass and the air around. Because of such quick cooling, the carbon gets retained and hard METAL stays in the weld. To overcome this, cast irons have to be preheated to 600°C.

Correct answer is (c) 12 MM

Easy EXPLANATION: In spot welding PROCESS, to BRING the heated parts in contact with one another, mechanical pressure is applied. This pressure can be of three types, by using foot lever, by providing air pressure or by using a HYDRAULIC cylinder. The use of these methods allows steel or other metal parts to be welded up to a thickness of 12 mm.

Right answer is (B) False

Explanation: Arc welding machines are able of working on both ALTERNATING current supply as well as direct current supply. But mainly arc welding machines WORK on D.C. supply only, where the positive terminal is CONNECTED to the welding machine.

The CORRECT OPTION is (a) 2000°C

The EXPLANATION: NONE.

The correct answer is (B) False

To EXPLAIN: None.

Right choice is (c) 1700°C

To explain I would say: City gas is a type of fuel gas that is USED for the welding of THIN sheets of steel which have a thickness of up to 3 mm. The FLAME TEMPERATURE of city gas is approximately about 1700°C.

Correct choice is (a) True

Explanation: Slags used in welding are GENERALLY a combination of silica materials and some carbonate compounds. In fusion welding, some AMOUNT of bead control has to be done, which is done by the slags, for this PURPOSE, to IMPROVE its performance, microelements LIKE manganese are added.

Correct CHOICE is (b) False

The explanation: Carbon steels are best treated using forge welding, resistance welding, arc welding or by gas welding. Carbon steels ESSENTIALLY cannot be FUSION WELDED, because, of the occurrence of cracks which may cause due to carbon pick up.

Correct answer is (a) 1 atm to 2 atm

To elaborate: In OXYGEN lance cutting, JET of oxygen is passed through steel PIPES, and by doing this, holes are PRODUCED. For doing this, the jet of oxygen is passed through the LANCER under the pressure of 1 atm to 2 atm.

Right answer is (c) 0.7%

For EXPLANATION I would say: For a steel to be TREATED by oxygen cutting PROCESS, the carbon content that should be available in terms of percentage composition is around 0.7%, that is, the steel that can be treated by this process is a high ALLOY steel.

Right answer is (a) True

For explanation I would say: A superheated melt OPERATES in this type of melt. The production of pipes, rail tracks, SHAFTS or BIG gears can be DONE using thermit pressure welding. Thermit welding is CALLED as fusion welding.

Right OPTION is (b) Crucible

To explain: Around the parts which are to be united, SUPERHEATED LIQUID steel is POURED, which then effects in FORMING the weld. This process, hence, is a fusion welding process. The part represented by the question mark is the crucible.

The correct answer is (b) False

For EXPLANATION: A flow of LARGE amount of current causes the generation of ARC blower. The space around the arc and the metal always experience magnetic fields, causing the currents to get squared. This results in an unstable behavior by the arc blower, which is THEREFORE not desirable for good WELDS.

Correct OPTION is (d) 800 to 3000A

Easiest EXPLANATION: An automatic WELDING machine has a high amount of capacity. Its capacity ranges in between 800 to 300A. This TYPE of machine is not portable and is suitably used for heavy welding processes.

The correct OPTION is (c) Strain relieving brittleness

To explain I would say: For the making of GOOD fabricated composition of a structure, metal with good weldability gets readily welded. Weldability INCLUDES the ability of the metal or the alloy to be having SOUNDNESS in its mechanical properties, METALLURGICAL compatibility of metal and serviceability of joint.

Correct OPTION is (a) 0.25% – 0.3%

EXPLANATION: Low carbon steels are the ones containing low amount of carbon in them, which does not REQUIRE preheating. The amount of carbon content NEEDED in low carbon steels, is 0.25% to 0.3%, if preheating is to be avoided.

The correct answer is (B) False

The explanation: CAST irons cannot be treated using oxygen cutting PROCESS. The reason being that the melting point of cast irons is a lot lower than its ignition temperature. The same cannot be SAID for HIGH alloy steels.

Correct choice is (c) 17 mm to 19 mm

To elaborate: In oxygen lance CUTTING, when the lance is MADE up of a thick WALL, with its outer diameter of 17 mm to 19 mm, and possessing an inner diameter of 8 mm to 6 mm, respectively, then good results can be obtained.

The CORRECT CHOICE is (B) Workpiece

To ELABORATE: NONE.

The correct option is (d) 150 kVA

To elaborate: SPOT welding can be used for all TYPES of ductile METALS. It can also be employed for structures of sheet metals, and can be APPLIED for MAKING of boxes and cans. For its applications, the maximum power that can be needed for this process is 150 kVA.

Correct option is (a) True

For explanation I would SAY: In gas welding, various metals like cast IRON, steel, aluminium, copper etc. can be used for joining operation. First they brought into a molten state and then a fusion is taking place between two pieces of metal in such a way that the point of fusion CLOSELY approaches the strength of the metal fused. In this process, the union or joint can be MADE even much STRONGER than the original.

The CORRECT CHOICE is (C) 3200°C

For EXPLANATION: NONE.

The correct choice is (b) False

For explanation I WOULD say: In gas welding, ACETYLENE is basically a colorless gas with a very distinctive odour and highly combustible when it is mixed with oxygen. Acetylene gas is FORMED by mixing the calcium carbide with water and then it is composed, which forms a compound of carbon and HYDROGEN having the chemical FORMULA C2H2.

The correct answer is (B) False

To explain I would say: In fusion welding, the welded pieces are not kept under pressure, instead they are welded first and then ALLOWED for some to COOL down. It is in pressure welding, that the welded pieces are kept under pressure for some time.

Correct answer is (b) 400°C

To EXPLAIN I would SAY: HIGH alloy steels are those steels which contain high amount of carbon in them. These ALLOYS need to be preheated before welding in order to AVOID cracking. The temperature up to which these alloys are preheated is 400°C.

The CORRECT choice is (b) False

To EXPLAIN: It can be counted among ONE of the DRAWBACKS of oxygen cutting process, that the metal which is to be treated must have its oxidizing TEMPERATURE higher than its melting temperature, otherwise the metal would get melted before getting oxidized.

Correct option is (B) LESS AMOUNT of plastics

For explanation I would say: While considering for explosive welding, the factors that one needs to understand is that, there has to be high relative velocity. There should be proper orientation and it needs to be KEPT under high amount of pressure.

Right choice is (d) Iron

To elaborate: The PROCESS of CARBON arc melting is widely used for copper and copper alloys, hence bronze and BRASS are treated by this method. Aluminium can also be treated likewise, but not iron METAL.

The correct choice is (b) 15 mm

Easy EXPLANATION: Oxy-acetylene processes are MAINLY used for the joining of metal sheets or for joining metal plates which are having a THICKNESS of 2MM to 50mm. When the thickness of the material is more than 15 mm, an additional filler metal is ADDED like a welding rod.

Right option is (a) Triangular

To EXPLAIN I WOULD say: A welding rod or a thermoplastic welding rod is used mainly in PLASTIC welding. The rod should not be very porous or it MAY CATCH voids. This rod has a cross sectional shape triangular or circular.

Right option is (d) Procedure of adding filler materials

The explanation is: When a particular metal or an alloy does not have desirable WELDING CHARACTERISTICS, then it can be corrected by proper FLUXING material, CORRECT filler material and a PERFECT welding procedure.

The correct answer is (b) False

Easiest explanation: In ULTRASONIC WELDING method, the PARTS which are to be joined, are kept clamping to one another in between of SUPPORTING member and the welding tip. In doing this, no current is REQUIRED to be passed through the metal, and usually, no heat is needed for this too.

Right choice is (d) Eutectoid fusion WELDING

The explanation: DIFFUSION welding is has three basic techniques which are INCORPORATED by it. These three basic techniques are, GAS – pressure welding, vacuum fusion welding and eutectic fusion welding.

The CORRECT OPTION is (b) 3000°C

To elaborate: Thermit welding is called as fusion welding. A superheated melt operates in this type of melt. The heat that is produced has the temperature APPROXIMATELY twice than that of the MELTING point of steel, which is about 3000°C.

The correct option is (a) True

Explanation: In flash butt WELDING process, there is a light contact between the EDGES. A high voltage is supplied when the FLASHING ACTION takes place. In this process, the metal that is forced out, is called as flash.

The correct option is (c) Sodium

Easy EXPLANATION: Non-consumable electrodes, are those electrodes which do not get consumed as the WELDING OPERATION proceeds. These electrodes are primarily made up of materials like carbon, GRAPHITE and tungsten.

Correct choice is (b) False

Explanation: In GAS WELDING, acetylene is used as a FUEL gas which is a hydrocarbon like other as propane, methane etc. However, it generally differs from those HYDROCARBONS in a manner that its molecule is made up of TWO carbon atoms and two hydrogen atoms. And the carbon atoms are joined with hydrogen atoms by making a triple bond.

The correct option is (C) Oxy-Acetylene cutting

The best explanation: AMONG the following, oxy-acetylene cutting is considered as a related PROCESS. Explosive is a TYPE of solid state WELDING. Electron-beam is a type of newer welding and oxy-hydrogen welding is a form of gas welding.